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Int. J. Mech. Eng. & Rob. Res. 2014 Ajin Elias Alex and Nadeera M, 2014

3D MODELLING AND ANALYSIS OF MICRO GASTURBINE COMPRESSOR BLADE

Ajin Elias Alex1* and Nadeera M1

*Corresponding Author: Ajin Elias Alex,ajinelias@gmail.com

Microturbines can be utilized in refrigerator, generator, air drier, etc., Micro turbine being small insize as compared to large turbine, such that less weight which reflects on pressure ratio, lowcost and easy maintenance. Design and analyze of the micro turbine compressor blade iscarried out in this thesis. With different material and rotational speed, compressor blade of themicro turbine is analyzed. A 3D Structural design of microturbine generating 120 KW of outputpower is modeled in Solidworks. Based on the given microturbine output power, the dimensionsand physical properties of the compressor blade were calculated. Titanium, Aluminium andStainless steel alloys, this materials effect on compressor blade are found out by carrying stressand modal analysis. Microturbine systems claimed many advantages over reciprocating enginegenerators, such as higher power to weight ratio, low pollution and having few moving part.Microturbines have many advantages, such that it may be designed with foil bearings and air-cooling operating without lubricating oil, coolants or other hazardous materials. Microturbinesare quicker to respond to output power requirement and also more efficient. Microturbines alsohave more efficiency at low power levels than reciprocating engines. The variation of rotationalspeed is a representation of various operating conditions, depending on the required output. Byanalysis software ANSYS 12, stress and modal analysis are done.

Keywords: Compressor blade, Microturbine, Vibrational analysis

INTRODUCTIONAxial flow compressors are used in mediumto large thrust gas turbine and jet engines. Thecompressor rotates at very high speeds addingenergy to the air flow while at the same timecompressing it into a smaller space. Thedesign of axial flow compressors is a great

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Int. J. Mech. Eng. & Rob. Res. 2014

1 Department of Computer Integrated Manufacturing, T.K.M College of Engineering, Kollam, India.

challenge, both aerodynamically andmechanically. The aerodynamic compressordesign process basically consist of mean lineprediction is the first step during compressorblade design.

Nowadays, the need of energy productionto be used for either industrial or several

Research Paper

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Int. J. Mech. Eng. & Rob. Res. 2014 Ajin Elias Alex and Nadeera M, 2014

transportations is in great demand. The typeof power generation has become the majorconcern because of its widespread need. Forthe concern of recent time needs, the suitablepower generation type is one which achievesa relatively better efficiency, low in cost, andsatisfied the demanding criteria.

Because of its critical role, it isunderstandable that innovation to a step furtheris needed. In a field where the major roleneeded and development costs both are themajor concerns, it was thought to build thesmallest possible gas turbine, and to explorewhether the device could be made into smallersize. The micro turbine is actually the scale-down of the large ordinary gas turbine system.

This is what gave birth to this project sincethe advantages of gas turbines are alreadyknown compared to other. This project dealswith designing of micro turbine compressorand the corresponding overall integrity analysisof the designated compressor.

Microturbine is definitely different from theusual large industrial gas turbine, althoughit has the same principal work and scale-

down from the large industrial gas turbine.Microturbines are quicker to respond tooutput power requirement and also moreefficient. The microturbine took in placebecause of the emerging need of innovationto the existing large gas turbine power plant,especially for the application of remote andlimited area to be placed. Microturbines areoperated at lower pressure ratios than largergas turbines.

Objective of StudyThe objective of this study is to model a microturbine compressor blade and conduct stressanalysis as well as vibration analysis basedon its rotation per minutes.

Materials

• Aluminum alloy.

• Stainless steel alloy.

• Titanium alloy.

Rotational Speed

• 40000 rpm

• 50000 rpm

• 60000 rpm

Scope of StudyThe design and the analysis of the structuresintegrity using finite element method isconducted. It is expected that the project willprovide the recommendation that can help toimprove the performance of compressordesign base on the previous analysis.

The scope of study consists of two majorparts. The first is to design the dimension ofthe compressor based on the given outputpower. The design is expected to be the mostoptimal dimension to that proposed output.

Figure 1: Microturbine

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Int. J. Mech. Eng. & Rob. Res. 2014 Ajin Elias Alex and Nadeera M, 2014

The second part is the analysis of thedesigned dimension of the compressor. Thispart is investigating the stress acting on thecompressor and conducting vibrationalanalysis of the model using the finite elementanalysis program. ANSYS is the software usedfor analysis. 3D model obtained from SolidWorks is imported to ANSYS in IGES format.

METHODOLOGYGeometrical ModellingSolidworks is used for the modelling purpose.This are the geometric parameter used formodelling.

AnalysisANSYS Workbench 12 is the software usedfor analysis. 3D model obtained from SolidWorks is imported to ANSYS in IGES format.

Compressor MaterialsThe material properties are assigned as partof the analyses. The material for thecompressor blade is chosen into threedifferent materials.

Figure 2: Methodology

Items Parameter Value

Shaft Diameter D(mm) 20

Impeller Inner Diameter D1(mm) 55

Impeller Outer Diameter D2(mm) 136

Impeller Thickness to Shaft h(mm) 42

Impeller Outflow Thickness b(mm) 4.825

Blade Degree (degree) 23.20

Blade Number - 11

Table 1: Compressor GeometryParameter

Source: Vyas and Basia (2013)

Titanium AlloyTi-b-120UCA Elastic modulus E(MPa) 0.102E6

Poisson ratio N 0.3

Density (kgm3) 4850

Ultimate TensileStrength UTS(MPa) 1675

AluminumAlloyAL-a7079 Elastic modulus E(MPa) 0.717E5

Poisson ratio N 0.33

Density (kgm3) 2740

Ultimate TensileStrength UTS(MPa) 558

Stainless SteelAlloy 304 Elastic modulus E(MPa) 0.193E6

Poisson ratio N 0.29

Density (kgm3) 8030

Ultimate TensileStrength UTS(MPa) 1147

Table 2: Different Material and its Details

Materials Items Parameter Value

Source: Vyas and Basia (2013)

Various conditions for analysis are:

Rotational Speed

• 40000 rpm

• 50000 rpm

• 60000 rpm

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Materials

• Aluminum alloy

• Stainless steel alloy

• Titanium alloy

– Stress Analysis

– Vibrational Analysis

RESULTSAnalysis Result of 60000 rpmThe Titanium alloy material at 60000 rpmcreates maximum stress of 6.178 × 108 Paand minimum stress of 2.22 × 106 Pa.

Figure 3: Stress Analysis of Titanium Alloyat 60000 rpm

Figure 4: Strain Analysis of Titanium Alloyat 60000 rpm

Figure 5: Stress Analysis of AluminiumAlloy at 60000 rpm

Figure 6: Strain Analysis of AluminiumAlloy at 60000 rpm

The Titanium alloy material at 60000 rpmcreates maximum strain of 0.0061 m/m andminimum strain of 2.18 × 10-5 m/m.

The Aluminium alloy material at 60000 rpmcreates maximum stress of 3.51 × 108 Pa andminimum stress of 1.10 × 106 Pa.

The Aluminium alloy material at 60000 rpmcreates maximum strain of 0.00489 m/m andminimum strains of 1.54 × 10-5 m/m.

The Stainless steel material at 60000 rpmcreates maximum stress of 1.02 × 108 Pa andminimum stress of 3.89 × 106 Pa.

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Figure 7: Stress Analysis of StainlessSteel 60000 rpm

Figure 8: Strain Analysis of StainlessSteel 60000 rpm

The Stainless steel material at 60000 rpmcreates maximum stress of 0.0052 m/m andminimum stress of 2.019 × 10-5 m/m.

Titanium Alloy Material (Ti-b-120UCA) =UTS/Fmax

= 1147 × 106 Pa/6.177 × 108 Pa

= 1.857

Aluminium Alloy Material (AL-a7079) =UTS/Fmax

= 558 × 106 Pa/3.509 × 108 Pa

= 1.590

Stainless Steel Alloy Material (STLAISI-304)

= 1675 × 106 Pa/1.021 × 108 Pa

= 1.640

Analysis Result of 50000 rpmThe Titanium alloy material at 50000 rpmcreates maximum stress of 4.33 × 108 Pa andminimum stress of 1.56 × 106 Pa.

The Titanium alloy material at 50000 rpmcreates maximum stress of 0.0042 m/m andminimum stress 1.53 × 10-5 m/m.

The Aluminium alloy material at 50000 rpmcreates maximum stress of 2.46 × 108 Pa andminimum stress of 7.75 × 105 Pa.

MaximumStress (Pa) 6.177 × 108 3.509 × 108 1.021 × 109

MaximumStrain (m/m) 0.00606 0.00489 0.00529

Table 3: Analysis Result of 60000 rpm

TitaniumAlloy

AluminiumAlloy

StainlessSteel Alloy

Safety Factor of this compressor model is:

Figure 9: Stress Analysis of TitaniumAlloy at 50000 rpm

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Figure 10: Strain Analysis of TitaniumAlloy at 50000 rpm

Figure 11: Stress Analysis of AluminiumAlloy at 50000 rpm

Figure 12: Strain Analysis of AluminiumAlloy at 50000 rpm

The Aluminium alloy material at 60000 rpmcreates maximum strain of 0.0034 m/m andminimum strain of 1.80 × 10-5 m/m.

The Stainless Steel alloy material at 50000rpm creates maximum stress of 7.16 × 108 Paand minimum stress of 2.73 × 106 Pa.

The Stainless Steel material at 50000 rpmcreates maximum strain 0.0037 m/m andminimum strain of 1.42 × 10-5 m/m.

Figure 13: Stress Analysis of StainlessSteel at 50000 rpm

Figure 14: Strain Analysis of StainlessSteel at 50000 rpm

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Safety Factor of this compressor model is:

Titanium Alloy Material (Ti-b-120UCA) =UTS/Fmax

= 1147 × 106 Pa/4.332 × 108 Pa

= 2.65

Aluminium Alloy Material (AL-a7079 = UTS/Fmax

= 558 × 106 Pa/2.461 × 108 Pa

= 2.27

Stainless Steel Alloy Material (STLAISI-304)= UTS/Fmax

= 1675 × 106 Pa/7.159 × 108 Pa

= 2.34

Analysis Result of 40000 rpmThe Titanium alloy material at 40000 rpmcreates maximum stress of 4.58 × 108 Pa andminimum stress of 1.75 × 106 Pa.

MaximumStress (Pa) 4.332 × 108 2.461 × 108 7.159 × 108

MaximumStrain (m/m) 0.00425 0.00343 0.00371

Table 4: Analysis Result of 50000 rpm

TitaniumAlloy

AluminiumAlloy

StainlessSteel Alloy

Figure 15: Stress Analysis of TitaniumAlloy at 40000 rpm

Figure 16: Strain Analysis of TitaniumAlloy at 40000 rpm

Figure 17: Stress Analysis of AluminiumAlloy at 40000 rpm

The Titanium alloy material at 40000 rpmcreates maximum strain of 0.0027 andminimum strain of 9.78 × 10-6 m/m.

The Aluminium alloy material at 50000 rpmcreates maximum stress of 1.57 × 108 Pa andminimum stress of 4.96 × 105 Pa.

The Aluminium alloy material at 40000 rpmcreates maximum strain of 0.0021m/m andminimum stress of 6.91 × 10-6 m/m.

The Stainless Steel material at 40000 rpmcreates maximum stress of 4.58 × 108 Pa andminimum stress of 1.75 × 106 Pa.

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Figure 18: Strain Analysis of AluminiumAlloy at 40000 rpm

Figure 19: Stress Analysis of StainlessSteel at 40000 rpm

Figure 20: Strain Analysis of StainlessSteel at 40000 rpm

MaximumStress (Pa) 2.772 × 108 1.575 × 108 4.582 × 108

MaximumStrain (m/m) 0.00272 0.00220 0.00240

Table 5: Analysis Result of 40000 rpm

TitaniumAlloy

AluminiumAlloy

StainlessSteel Alloy

Safety Factor of this compressor model is:Titanium Alloy Material (Ti-b-120UCA) =

UTS/Fmax= 1147 × 106 Pa/2.772 × 108 Pa= 4.138

Aluminium Alloy Material (AL-a7079) =UTS/Fmax

= 558 × 106 Pa/1.575 × 108 Pa= 3.54

Stainless Steel Alloy Material (STLAISI-304)= UTS/Fmax

= 1675 × 106 Pa/4.582 × 108 Pa= 3.66

Various Rotational Speed Results

Titanium Alloy Analysis

MaximumStress (Pa) 2.772 × 108 4.332 × 108 6.177 × 108

Safety factor 4.13 2.65 1.86

Table 6: Analysis Result of Titanium Alloy

40000 50000 60000Speed

The Stainless Steel material at 60000 rpmcreates maximum stress of 0.0024 m/m andminimum strain of 2.22 × 10-6 m/m.

Figure 21: Graph Showing Analysis Resultof Titanium Alloy

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Aluminium Alloy Analysis

Stainless Steel Alloy MaterialAnalysis

MaximumStress (Pa) 1.575 × 108 2.461 × 108 3.509 × 108

Safety factor 3.54 2.27 1.59

Table 7: Analysis Result of Aluminium Alloy

40000 50000 60000Speed

Figure 22: Graph Showing Analysis Resultof Aluminium Alloy

MaximumStress (Pa) 4.582 × 108 7.159 × 108 1.021 × 109

Safety factor 3.66 2.34 1.64

Table 8: Stainless Steel Alloy MaterialAnalysis

40000 50000 60000Speed

Vibrational AnalysisThe Titanium alloy material at 4428.3 rpmcreates vibration of 4428.3 Hz frequency andmaximum deflection of 1.69 mm.

Figure 23: Graph Showing Analysis Resultof Stainless Steel Alloy

Figure 24: Vibrational Analysisof Titanium Alloy at 40000 rpm

Figure 25: Vibrational Analysisof Aluminium Alloy at 40000 rpm

The Aluminium alloy material at 40000 rpmcreates vibration of 4940.8 Hz frequency andmaximum deflection of 3.20 mm.

The Stainless Steel alloy material at 40000rpm creates vibration of 4940.8 Hz frequencyand maximum deflection of 1.53 mm.

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Comparison Table of VariousMaterials at 40000 rpmThe Titanium alloy material at 40000 rpmcreates a low vibration of 4428.3 Hz frequency

Figure 26: Vibrational Analysisof Stainless Steel at 40000 rpm

Frequency(Hz) 4428.3 4940.8 4730.5

Deformation(mm) 1.69 3.21 1.53

Table 9: Comparison Table of VariousMaterials at 40000 rpm

TitaniumAlloy

AluminiumAlloy

StainlessSteel

Figure 27: Vibrational Analysisof Titanium Alloy at 50000 rpm

Figure 28: Vibrational Analysisof Aluminium Alloy at 50000 rpm

Figure 29: Vibrational Analysisof Stainless Steel at 50000 rpm

as compared to Aluminium Alloy and Stainlesssteel.

The Titanium alloy material at 50000 rpmcreates vibration of 4462.8 Hz frequency andmaximum deflection of 2.02 mm.

The Aluminium alloy material at 50000 rpmcreates vibration of 4971.4 Hz frequency andmaximum deflection of 1.97 mm.

The Stainless Steel alloy material at 50000rpm creates vibration of 4462.4 Hz frequencyand maximum deflection of 1.25 mm.

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Comparison Table of VariousMaterials at 50000 rpmThe Titanium alloy material at 50000 rpmcreates a low vibration of 4462.8 Hz frequencyas compared to Aluminium Alloy and Stainlesssteel.

Comparison Table of VariousMaterials at 60000 rpm

Frequency(Hz) 4462.8 4971.4 4762.4

Deformation(mm) 2.02 2.66 1.25

Table 10: Comparison Table of VariousMaterials at 50000 rpm

TitaniumAlloy

AluminiumAlloy

StainlessSteel

Figure 30: Vibrational Analysisof Titanium Alloy at 60000 rpm

Figure 31: Vibrational Analysisof Aluminium Alloy at 60000 rpm

Figure 32: Vibrational Analysisof Stainless Steel at 60000 rpm

Frequency(Hz) 4503.2 5007.7 4792.9

Deformation(mm) 1.97 2.66 1.59

Table 11: Comparison Table of VariousMaterials at 60000 rpm

TitaniumAlloy

AluminiumAlloy

StainlessSteel

The Titanium alloy material at 60000 rpmcreates a low vibration of 4503.2 Hz frequencyas compared to Aluminium Alloy and Stainlesssteel.

The Titanium alloy material at 60000 rpmcreates vibration of 4540.3 Hz frequency andmaximum deflection of 1.97 mm.

The Aluminium alloy material at 60000 rpmcreates vibration of 5007.7 Hz frequency andmaximum deflection of 2.66 mm.

The Stainless Steel alloy material at 60000rpm creates vibration of 4792.9 Hz frequencyand maximum deflection of 1.59 mm.

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CONCLUSIONThe compressor blade is modelled by using3D modeling Software Solid works 2013. Inthis case stress analysis and vibrationalanalysis of different materials is carried outusing analysis software ANSYS 12.

This analysis shows that Titanium alloyblade gives better safety factors comparedto other alloys. The vibration characteristicsfrom model analysis were also good for thesame alloy. The simulation showed that thestresses are concentrated on the bladeattachment to the hub. A better safety factorwould be obtained when the rotationalspeed is decreased. The simulat ionshowed that the stresses are concentratedon the blade attachment to the hub, causedby the centrifugal stresses. The countermeasure for this problem is to apply thef i l let radius th ickening of the bladeattachment to the hub.

Another point observed is that a higherrotational speed will result in greaterstresses to be borne by the structure, whichindicates that a better safety factor would beobtained when the rotational speed isdecreased.

Considerations about the limiting rotationalspeed are also of importance. Because of theneed to have a particular output power, thedesignated rotational speed needs to bepredicted, since structural strength is limitedby the various rotational speeds. Thus for thispurpose, Titanium alloy, with a much higherultimate tensile strength compare to StainlessSteel and Aluminium alloy, is thus the safematerial to be used because they have thehigher Young’s modulus (E).

FUTURE SCOPEEven though Titanium Alloy have betterproperties comparing with others when costfactor come into consideration then it is costly.For future works, new material or compositematerial has to be found out with low cost andmore efficient.

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